hw/core/register: Add more 64-bit utilities

hw/core/register: Add more 64-bit utilities

We already have some utilities to handle 64-bit wide registers, so this just
adds some more for:
- Initializing 64-bit registers
- Extracting and depositing to an array of 64-bit registers

Signed-off-by: Joe Komlodi <joe.komlodi@xilinx.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 1626805903-162860-2-git-send-email-joe.komlodi@xilinx.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>